Generally, a substation for electric railway converts alternating-current power supplied from an electric power company or alternating-current power supplied from a power plant owned by an electric railway company into direct-current power, and supplies to feeder lines. The direct-current power supplied to the feeder lines passes through aerial power lines, and is supplied into electric vehicles by way of pantographs. Or the direct-current power is supplied from the feeder lines to the electric vehicles by way of a third rail. The electric vehicle supplies the provided electric power to a traction motor (rotary motor or linear motor) by way of an electric power control device mounted on the vehicle, and the electric energy is converted into a traction energy, and the vehicle is driven.
The amount of energy consumed by an electric vehicle varies with the running state of the vehicle. Specifically, the electric vehicle consumes a large amount of electric power in a short time at the time of acceleration. As a result, the voltage of the power line or the third rail, and further the voltage of the feeder line drops temporarily. To cope with such temporary voltage drop, a railway facility accommodating electric vehicles having a regenerative function utilizes the rotary motor or linear motor for traction as a generator at the time of deceleration, and converts the running energy of the electric vehicle into an electric energy in order to recover an electric power. The recovered electric power is utilized to cover up for the temporary voltage drop of the supply voltage.    Patent document 1: JP 2000-341874 A    Patent document 2: JP 2001-260719 A    Patent document 3: JP 2002-2334 A